Its not just Mibbit as FFH wasn't connecting on mIRC earlier for a day (cannot connect to server). I just tried and its working again right now.

<&Angel> if WotL is your preference, 99 times out of 100, you can't be trusted to know how to use a toilet properly<~Xifanie> Weazel has a degree in bathroomonics<&Angel> everyone who wants to mod WotL exclusively is pants on head retarded

I've been getting that error for months. Something in the way that Pale Moon (fork of Firefox with better UI) deals with certificates? In any case I don't expect this to be a problem anyone here can fix, just something to be aware of if someone else has the same issue.